The present invention is a stable water-in-oil emulsion and in particular a water-in-oil emulsion wherein the oil contains as a component one or more organopolysiloxanes and at least one of the organopolysiloxanes is an elastomer.
Emulsions are generally formed from at least two liquid phases which are immiscible so that at least one of the phases is dispersed in fine form throughout the other phase(s). While emulsions are often formed by many components in complex relationships, they can be broadly classified as either oil-in-water or water-in-oil emulsions, depending on which of the phases comprises the dispersed inner phase and which is the continuous outer phase. In this context, an oil may be defined as any material immiscible with water and capable of forming an emulsion with water. Various agents are used to retard or inhibit the separation of emulsions into their constituent phases and these agents may determine the type of emulsion formed. Additionally, the nature of the emulsion can be reversed depending on the agent employed.
Generally speaking, water-in-oil emulsions have been considered less desirable than oil-in-water emulsions because the former have been associated with a greasy feel while the latter are perceived as having a more aesthetically pleasing feel and texture.
Water-in-oil emulsion systems do have desirable properties. However, one drawback to the use of such systems for commercial products is the difficulty associated with maintaining such systems stable against separation.
Irrespective of the desirable properties, unstable compositions of water-in-oil emulsions are of little interest for commercial products. Further, stabilized emulsions which destabilize with the incorporation of customary additives and necessary processing are likewise of little value.
Organopolysiloxanes have, in recent years, gained widespread acceptance and have found a broad spectrum of fields of use such as in, i.e. foodstuffs, medical treatments, personal care compositions including cosmetics, water repellents, lubricants, etc. Within this broad class of materials are compounds known as organopolysiloxane elastomers. While such elastomers have varying and interesting properties, they are often incompatible with other components commonly used in various fields rendering these materials useless or marginally useful for limited applications. Thus it is highly desirable to produce stabilized water-in-oil emulsions wherein the oil component is based on, or comprises, an organopolysiloxane elastomer.
Organopolysiloxanes are a well known class of compounds of the general formula: ##STR1## R being the same or different monovalent organic radicals such as alkyl or aryl groups. Organopolysiloxanes are hetero-chain polymers in contrast to those having a backbone which contains only carbon.